The manufacture of microelectromechanical system (MEMS) devices is generally well-known, and there are numerous devices used in different applications and numerous methods of making those devices. An example of a method of manufacturing a MEMS device is contained in U.S. Pat. No. 6,925,710 titled “METHOD FOR MANUFACTURING MICROELECTROMECHANICAL COMBDRIVE DEVICE” TO Scalf et al., herein incorporated by reference. An example of a MEMS device is contained in U.S. Pat. No. 6,705,166 titled “SMALL SIZE, HIGH CAPACITANCE READOUT SILICON BASED MEMS ACCELEROMETER” to Leonardson, herein incorporated by reference.
The Leonardson accelerometer provides an inexpensive force measurement device having high pick-off sensitivity in a high-G input range which can operate in a high-G shock environment by providing a capacitance pick-off force sensor having a proof mass with spaced-apart tooth-type electrodes (i.e., a comb structure) that is suspended by an annular suspension member.
One limitation of current methods of manufacturing the comb structure of the Leonardson accelerometer is the practice of manufacturing the proof mass and the cover plate separately, each including tooth-type electrodes, and then mechanically assembling the proof mass and the cover plate. This method requires mechanical alignment of the teeth of the proof mass with the recesses of the cover plate, and vice versa. Mechanical assembly in this way can achieve close tolerances between cover plate electrodes and adjacent proof mass electrodes, but not tolerance levels needed for comb drive devices. A need exists, therefore, for manufacturing methods that will allow smaller tolerances between adjacent electrodes than permitted by current manufacturing processes that use mechanical assembly.